Device for supervising the internal structure of solid bodies and the content thereof



March 6, 1962 N. E. STRANDELL 3,024,363

DEVICE FOR SUPERVISING THE INTERNAL STRUCTURE OF SOLID BODIES AND THE CONTENT THEREOF Filed April 27, 1954- 2 Sheets-Sheet 1 IN V EN TOR.

BY NlLS EDVARD STRANDELL ATTQRNEY March 6, 1962 N. E. STRANDELL 3,024,363

DEVICE FOR SUPERVISING THE INTERNAL STRUCTURE OF SOLID BODIES AND THE CONTENT THEREOF Filed April 1954 2 Sheets-Sheet 2 FIG.

I I I I I I I I I I I I I I I I I I I I II\ I I I I I KI" LO INVENTOR. NILS EDVARD STRANDELL BY M1 5.

AT TORN EY United States Patent 3,024,363 DEVICE FOR SUPERVISING THE INTERNAL STRUCTURE OF SOLID BODIES AND THE CONTENT THEREOF Nils Edvard Strandell, Karlskoga, Sweden, assignor to Aktiebolaget Bofors, Bofors, Sweden, :1 Swedish corporation Filed Apr. 27, 1954, Ser. No. 426,015 Claims priority, application Sweden Apr. 28, 1953 22 Claims. (Cl. 25083.3)

The present invention relates to a device for supervising by means of radiation the internal structure or the content of solid bodies, more particularly, to a device for detecting flaws in the internal structure of solid bodies including metal bodies and the presence of foreign substances or cavities in material contained in a body.

It is often necessary, or at least desirable to examine the internal structure of solid bodies such as construction elements for instance, girders, beams or columns as to flaws, or material filled in containers as to the presence of cavities and impurities. A preferred field of application of the invention is the supervision of the explosive charge contained in shells and other missiles. The explosive charge may contain impurities such as water, flakes of explosive substances, wood chips, etc. Experience has shown that in practice it is very difficult if not impossible, to avoid the occasional inclusion of such impurities. Furthermore, cavities may be formed within the charge when and while the shell casing is being filled with the explosive. The presence of such impurities and cavities may cause pre-ignition of the charge when the shell is fired, possibly resulting in injuries to the gun crew and bursting of the gun barrel.

In view of the aforementioned great danger and other reasons, it is standard practice to check all the shells of a production run of certain types of shells rather than to make random tests.

It is known to use X-ray photography to conduct the aforedescribed examinations. However, X-ray photography is inherently slow and requires highly trained personnel so that when applied to mass production items, it tends to create a bottleneck in the production line.

Accordingly, one of the principal objects of the invention is to provide a novel and improved device of the general type above referred to, which permits rapidly and accurately to detect flaws in solid bodies and the presence of cavities or impurities in material contained in such bodies by subjecting the same to a radiation such as an X-ray radiation or a radio active radiation.

Another object of the invention is to provide a novel and improved device of the general type above referred to, the operation of which is so simple that it can be readily handled by untrained or semi-trained personnel.

Still another object of the invention is to provide a novel and improved device which by reason of its operational simplicity and reliability lends itself to inclusion in a mass production line.

The device according to the invention is particularly suitable for the supervision of bodies presenting rotation symmetry such as the already mentioned shells.

According to a now preferred embodiment of the invention, the device comprises a support which permits to impart to the body to be examined rotary and/or axial movements, a source of radiation, the radiation of which is directed upon said body, a mechanical beam splitter for splitting the radiation emanating from said source into at least one pair of radiation beams either anterior or posterior of the body to be examined, a pair of radiation sensitive means generating differential voltages corresponding to non-uniform changes experienced by the beams when traversing through said body due to varia- 3,024,363 Patented Mar. 6, 1962 tions in the internal structure or in the content thereof, and indicating means controlled by said differential voltages.

Further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the accompanying drawing a now preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

FIG. 1 shows diagrammatically a device for supervising a body such as a shell presenting rotation symmetry, and

FIG. 2 is a circuit diagram of the radiation sensitive means of the device and the electronic control means associated therewith.

Referring first to FIG. 1 in detail, the device according to this figure comprises a support generally designated by 1 including a shaft 2 mounting disc 1' for-supporting a shell 21 the explosive charge of which is to be examined. Shaft 2 is axially movable and coupled with conventional drive means (not shown) disposed in the casing of support 1 for imparting axial movements to the shaft. Disc 1 supports four hearings in which are rotatably mounted four shafts, shafts 6, 7 and 8 and three of the bearings are visible, the fourth shaft and the fourth bearing being concealed by shell 21. Each of the shafts mounts a gear 9, 10 and 11 respectively. These gears are in mesh with a gear 12 fixedly seated on a shaft 13 disposed coaxially with disc 1' and shaft 2 which is hollow for this purpose. Shaft 13 is rotatable and is driven by conventional rotary drive means also disposed in the casing of support 1. A common drive means may of course be provided to produce the required axial and rotary movements. Rotation shaft 13 is transmitted to shafts 6, 7 and 8. l

The drive means for imparting an axial movement to shaft 2 and disc 1' supported thereon should be visualized as being controlled by a switch 14 the operation of which connects or disconnects the axial drive means. The speed of the drive means may be regulated by means of a setting knob 15. Similarly, the drive means for imparting a rotation to shaft 13 are controllable by a switch 16 and may be regulated as to speed by means of a setting knob 17 which also permits to reverse the rotation of shaft 13.

Instead of providing manually operable control means 14 to 17 inclusive, the axial movements of shaft 2 and the rotation of shaft 13 may of course also be controlled by a suitable pattern or program component incorporated in the device or the production line. Automatic controls of this type are well known in the art and a detailed description thereof is not essential for the understanding of the invention.

It will be evident that the invention is not limited to the illustrated exemplification of the support. It is only essential that means are provided capable of imparting an axial and/or rotational movement to the shell or other body to be examined. Such support means may take the form of a cup in which is placed the lower or rear part of the shell and held in position. The cup .is coupled with a drive shaft to which an axial and a portions different in thickness, as is generally true for a shell casing, provisions need to be made to compensate for such variations in thickness, the amount of a radiation penetrating the shell being obviously affected by the thickness of the casing wall. Accordingly, compensating means 23 are provided in the path of the radiation, either as shown anterior of shell 21 or posterior thereof. The compensating means as exemplified comprise a stepped wedge which is secured to disc 1' by any suitable means so as to participate in the axial movement thereof thereby remaining stationary relative to the shell. The steps of the wedge correspond to the variations in the thickness of the wall of the shell so that the combined thickness of the shell wall and the wedge as seen by the radiation is substantially uniform over the entire length of the shell.

A source of radiation 24 is disposed to the right of shell 21. This source may be visualized by an X-ray tube or a suitable device emitting radio-active isotope. The radiation is first framed by a mask 25 the aperture of which is such that the shell becomes the target for a beam of suitable shape.

After passing through the wedge and the shell the wide beam framed by mask 25 is split by a mechanical beam splitter 26. This beam splitter has two pairs of slots 27, 28 and 29, 30. The two slots of each pair are parallel and symmetrically disposed to form outer beams or pencils 31 and 32 and inner beams or pencils 33 and 34. Beams 31 and 32 are directed to impinge upon two radiation sensitive means 35 and 36 shown as phototubes. Each of the tubes comprises a fluorescent component 37 and 38 respectively for instance sodium iodide, component 37 being impinged upon by beam 31 and component 38 by beam 32. When impinged by the radiation beams the fluorescent components begin to emit a radiation which activates the phototubes with which they are associated. Both the phototubes 35 and 36 are preferably continuously illuminated by a light bulb 39 of substantially uniform intensity. Such exposure of the phototubes to a constant illumination results in a certain low load of the tubes which assists in avoiding amplification changes which may arise upon transition from a condition of inactivity to a load condition.

Phototubes 35 and 36 may be of conventional design. This may be visualized as photomultiplier tubes. A tube of this type comprises a photo-cathode, several dynodes and an anode. The dynode nearest the photocathode is generally referred to as the first dynode and the dynode most distant from the photocathodes as the last dynode. The electrodes in the phototube obtain their voltages from a voltage divider so connected that the anode has a higher voltage than the last dynode and that this last dynode has a higher voltage than the second to last dynode and so on. The voltage distribution between the electrodes of the tube is such that the dark current, that is, the current obtained when the phototube is not illuminated is at a minimum taking in consideration the prevailing amplification.

A photomultiplier tube functions in such a manner that if for example the photocathode emits one electron, this electron impinges upon the first dynode which by secondary emission will emit about eight electrons. These electrons will impinge upon the second dynode and each one of the eight electrons will effect a secondary emission of the second dynode resulting in the emission of eight times eight electrons. As a result, an electron emitted by the cathode will be re-emitted by successive dynode until the electrons emitted by the last dynode are collected by the anode. Hence, if the cathode is exposed to a radiation from the fluorescent material associated with the phototube, a larger or smaller number of electrons, depending upon the intensity of the radiation emitted by the fluorescent substance, will be emitted by the photocathode thereby controlling the flow of current between the last dynode and the anode.

Conductors 40 and 41 connect the two phototubes 35 and 36 to a control unit 42 which will be explained in detail in connection with FIG. 2. Unit 42 is connected by a conductor 43 with an indicator 44 and by a conductor 45 with a switching device disposed within the casing of support 1 and controlled by the axial up and down movement of shaft 2.

A second beam splitter 46 is disposed posterior of tubes 35 and 36 as seen in the direction of the radiation. This beam splitter includes two slanted parallel slots 47 and 48 aligned with slots 29 and 30. Slots 47 and 48 serve to direct beams 33 and 34 to a second pair of phototubes 49 and 50. These tubes are similar to tubes 35 and 36 and each provided with a radiation sensitive component 51 and 52 respectively containing a fluorescent substance. A source of light 53 of substantially constant intensity preferably illuminates both tubes 49 and 50 through a light conducting tube or channel 54 to maintain the phototubes at a certain low load to avoid amplification changes during the transition from the inactive condition to a load condition.

Tubes 49 and 50 are connected by conductors 55 and 56 respectively to a control unit 57 similar to control unit 42. Unit 57 is connected through a conductor 58 to indicator 44 which is hence common to both control units 42 and 57. A conductor 59 connects unit 57 to the switching device disposed in the casing of support 1 and controlled by the axial up and down movements of shaft 2.

For sake of simplification, only two pairs of phototubes are shown in FIG. 1. However, additional pairs of tubes could be provided in a similar arrangement. In such case the first beam splitter 26 has to be provided with as many pairs of slots as there are successive pairs of phototubes.

It should further be understood that it is within the scope of the invention to use radiation sensitive means other than phototubes, such as photocells, Geiger-Muller tubes or ionization chambers.

It is further within the scope of the invention to replace the transversely arranged pairs of slots in the beam splitters by vertically displaced pairs of slots or by a combination of transversely and vertically displaced slots.

Referring now to FIG. 2, this figure shows phototubes 35 and 36 with their fluorescent components 37 and 38 respectively, control unit 42 and indicator 44. The circuit system of unit 42 is shown within the dotted frame line. As already mentioned, phototubes 49 and 50 are identical with tubes 35 and 36 and control unit 57 is identical with control unit 42 so that the entire circuit arrangement of the device is apparent from FIG. 2.

The photocathode of tube 35 is connected by a conductor 64 through a variable resistor 66 and a fixed resistor to one terminal of a source of voltage, the said terminal being at a potential of approximately -1000 volt. A voltage divider is included in a ground connection of the photocathode of tube 35 and is connected with the first, second, etc. up to the next to last dynode of the tube in such a manner that the second to last dynode is at a potential of approximately volt and the other dynodes at progressively higher negative potentials. The phototube is grounded by a conductor 62.

The photocathode of phototube 36 is connected by a conductor 65 through a variable resistor 68 to the aforementioned terminal at a potential of --l000 volt and is grounded through conductors 63 and 62. A voltage divider is included in a connection between the photocathode and ground. All the dynodes of tube 36 are connected with this voltage divider in a manner such that the last dynode is at a potential approximately corresponding to the potential of the next to last dynode of phototube 35.

A conductor connects the anode of phototube 35 to one terminal of a second source of voltage, the said 3,02e,ses

terminal having a potential of approximately +100 volt. The anode of phototube 36 and the last dynode of phototube 35 are interconnected by conductors 60 and 61 and grounded through a fixed resistor 75 and a voltage divider. This voltage divider comprises fixed resistors 70 and 72 and a variable resistor 74. A positive and a negative potential are applied to the voltage divider through fixed resistors 71 and 73 connected in series with resistors 70 and 72 respectively. Resistor 75 is connected with a slider contact slidable on resistor 74 of the voltage divider.

When light emitted by the fluorescent components 37 and 38 impinges upon the photocathodes of tubes 35 and 36 respectively, a current I will flow from the last dynode in phototube 35 and also a current I to the anode of phototube 36. By varying the total voltages across the voltage dividers to which the dynodes of the phototubes are connected, the amplification in the phototubes can be varied and hence the strength of the aforesaid currents.

When the two components 37 and 38 are impinged upon by radiation beams such as X-ray beams of equal intensity, it is advisable to change the amplification in the phototubes by setting the variable resistors 66 and '68 so that currents I and I, are balanced thereby making currentless resistor 75. If now the intensity of one of the beams becomes momentarily greater than that of the other beam, the balance of currents I and I is upset. As a result, a negative or a positive voltage pulse passe-s across resistor 75 which is fed to an amplifier 77 through a capacitor 76. A capacitor 69 connected between one end of resistor 75 and ground, capacitor 76 and resistor 75 constitute a filter network as is apparent from the diagram. In this network, capacitor 69 acts as a short circuit for the high frequency currents generated by the static fluctuations superimposed upon currents I and I,,. Capacitor 76 forms a barrier for the low frequency voltages across resistor 75 resulting from the slowness of the amplification changes in the phototubes.

Voltage pulses within a desired frequency band pass over capacitor 76 to amplifier 77. This amplifier preferably includes several RC-filter links'for the purpose of sharpening the passed frequency band. The amplifier is connected directly to one of the anodes of a double diode 78 and to the other anode of this diode through a phase shifter. As can be seen in FIG. 2., the amplifier is connected through a capacitor 79 and a resistor 80 to the grid of a triode 81. The grid is grounded through a resistor 80'. The anode of the triode is connected by a conductor 83 to the aforementioned second anode of diode 78. A suitable voltage is applied to the anode of triode 81 through a resistor 84. The cathodes of the double diode 78 are connected through a contact arm 85 of a relay 86 to the switching device disposed within the casing of support 1 and controlled by the axial up and down movement of shaft 2.

When the aforementioned volt pulses generated by exposure of components 37 and 38 to radiation of unequal intensity are positive after having passed through the amplifier, they are conducted directly to the double diode 78. If the pulses are negative, they are fed to the double diode through the phase shifter. From the double diode, the pulses are transmitted to the indicator through the relay arm 85. The indicator is arranged to indicate that the two phototubes are exposed to unequal radiation and may be equipped for this purpose with suitable means such as a lamp which is illuminated or an activated pointer coacting with an appropriately calibrated scale.

A blocking voltage is preferably applied by conventional means suitable for the purpose to the cathodes of double diode 78. This blocking voltage permits only the passage of that portion of the pulses coming from the amplifier to the double diode which exceeds the blocking voltage. As a result, only such pulses, the amplitude of which is above a predetermined level are capable of actuating indicator 44.

To assure a satisfactory operation of the two phototerminal of a suitable source of potential.

.obtains a large amplitude.

tubes, it is advantageous to match asclosely as possible the amplification in the two tubes. To this end, a separate automatic balancing system has been provided which, by feeling the voltage across capacitor 69, regulates one of the voltages applied to the photocathodes of the two tubes.

When the phototubes are in perfect balance, currents I and I will neutralize each other and no current Will flow through resistor 75. To obtain a satisfactory operation of the balancing system, it is necessary that there is a negative voltage of a few tenths of a volt on the nongrounded side of capacitor 69 when the system is in balance. This voltage is obtained from voltage divider 70, 72, 74 by an appropriate setting of the slider contact coacting with resistor 74. The setting of this slider contact permits also to compensate for any leakage currents which may pass through conductors 60 and 61. A chopper 87 such as a so-called Brown converter, is connected across the terminals of capacitor 69. The reed or tongue 88 of the chopper is connected to the non-grounded side of capacitor 69 and one of the chopper contacts is grounded through a resistor 89. The chopper comprises a coil 89' which is energized with alternating current from'a suitable A.-C. source. A second contact of the chopper is connected to one of the cathodes of resistor 91 connected in parallel with an also grounded capacitor 92. The two anodes are further connected to the grid of the first triode portion of a double triode 93 which serves to amplify, in two stages, a signal received from the double diode 90. The cathode of said first triode portion is grounded through a resistor 94 in parallel with a capacitor 95. The anode of the first triode portion is connected through a resistor 96 with the positive The anode of the second triode portion is connected to the same source of potential through a resistor 97 and also to the primary of a transformer 98. The anode of the first triode portion is further connected through a capacitor 99 to the grid of the second triode portion. The grid of this latter triode portion is grounded through a resistor 100 and also through a diode 101. The purpose of this latter diode is to prevent excessive positive voltages at the grid of the second triode portion of triode 93. Such excessive voltages may occur when the applied signal The cathode of the second portion of triode 93 is grounded through a resistor 102.

The secondary of transformer 98 is connected with one end to one of the cathodes of a detector circuit including a double diode 103. The two diode portions are connected in series to provide a high blocking resistance. The other end of the secondary is connected to a filter circuit including a capacitor 104 and a resistor 105. This filter circuit is also connected to one of the anodes of the double diode 103 in the detector circuit and to a capacitor 108 connected in parallel with a resistor 107. Capacitor 108 and resistor 107 form a network having a very high time constant. One side of capacitor 108 is connected to one side of variable resistor 66 and to the cathode of a triode 106. The grid of this triode is connected to the other side of capacitor 108.

The anode of triode 106 is connected through a measuring instrument 109 to the negative terminal of a source of potential having a lower negative voltage than the high negative voltage applied to the cathode of triode 106 through resistor 67.

The just described circuit arrangement constitutes a stabilization system which permits an automatic control of the voltage impressed upon the grid of triode 106 which voltage is directly dependent upon the voltage at the nongrounded side of capacitor 69. By varying the voltage of the grid of triode 106, the anode current flowing through triode 106 can be regulated. The regulation of this current in turn permits to adjust the voltage drop across resistor 67 and hence to control the cathode voltage and the amplification in phototube 35. This controls functions in a manner such that a slow change in the amplification in one of the phototubes is practically completely neutralized.

The device as hereinbefore described, operates as follows:

Let it be assumed that disc 1 is placed in its uppermost axial position. The shell 21 is then put in the position of FIG. 1 and disc 1 is caused to move into its lowermost position. Starting from this latter position the upward movement of disc 1 is commenced and also the rotation of shaft 13 causing a simultaneous continuous rotation of the shell. As a result, the shell is exposed to the X-ray radiation from X-ray tube 24. For the purpose of investigating the explosive charge filling the shell, it may be assumed that the wall of the shell is flawless. The compensatory wedge 23 placed in front of the shell equalizes the thickness of the shell wall-the said wall having actually a diiferent thickness at different portions of the shell casing-as seen by the radiation. Consequently, the radiation will be uniformly absorbed by the shell casing and the compensatory wedge so that the two pairs of radiation beams formed by beam splitter 26 will be of equal intensity. Hence, the two pairs of phototubes 35, 36 and 49, 50 are equally excited. No voltage is fed to the amplifier 77 in control unit 42 or to the corresponding amplifier in control unit 57.

The same situation obviously prevails when the explosive charge in the shell is free of cavities or impurities.

Let it now be assumed that cavities and/or impurities are present in the explosive charge. Such cavities or impurities will cause a corresponding unequal absorption of the radiation when passing through the shell.

' Slots 27 and 28 of beam splitter 26 are so disposed that beams 31 and 32 formed by these slots pass through the outer portion of the body formed by the explosive within the shell casing. This outer portion has a tubular configuration. The cylindrical inner portion of the explosive is examined by the radiation beams 33 and 34 framed by slots 29 and 30. As a result of such unequal absorption of the radiation, the phototubes or more spe cifically the fluorescent components 37, 38 and 51, 52 thereof, are impinged upon by beams of different radiation intensities. Consequently, the phototubes are differently excited which results in the generation of a corresponding differential voltage to amplifier 77 or to the amplifier associated with control unit 57. The control units 42 and 57 in turn control indicator 44 correspondingly. The indicator is preferably so designed that it begins to indicate from the moment it receives a voltage until a new measuring cycle is commenced.

Relay 86 coacting with control unit 42 and the corresponding relay coacting with control unit 57 are so controlled by the aforementioned devices within the casing of support 1 that indicator 44 is connected with the two double diodes of control uni-ts 42 and 47 respectively for that part of the movement of disc 1 during which it is desirable to examine the shell content by the device.

It will be apparent from the previous description that the device according to the invention is not limited to the examination of the explosive charge in shell casings but may be advantageously employed wherever similar condit-ions prevail.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modificaions may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A device for detecting the internal wall structure of hollow elongated rotation symmetric bodies having a wall varying in thickness along the length of said body and the presence of cavities in material filling said bodies, said device comprising rotatable and axially movable support means for supporting a body to be detected in a predetermined position, a source of radiation for radiating a body placed on said support means, a pair of radiation sensitive means, said support means being disposed between said source and said radiation sensitive means, mechanical beam splitting means between said source and said radiation sensitive means for splitting the radiation emanating from said source and passing through said body into at least two beams and directing said beams upon said radiation sensitive means, each of said beams impinging upon a respective one of said radiation sensitive means, the impinging radiation intensity of said beams being controlled by the internal structure of the respective traversed body portion, indicating means controlled by both said radiation sensitive means so as to indicate a differential in the radiation impinging thereupon, said differential being indicative of the internal structure of the body, and compensating means interposed between the source of radiation and the radiation sensitive means and mounted stationarily relative to said support means and to a body supported thereon in said predetermined position, said compensating means including a wall member varying in thickness, the dilferences in the thickness of the wall member being correlated with the differences in the thickness of said body so that the thickness of the compensating wall member and the configuration of the body as seen by the source of radiation are substantially uniform.

2. A device according to claim 1, wherein the said beam-splitting means are disposed between the support means and the radiation sensitive means.

3. A device according to claim 1, wherein the said support means comprise roller means engageable with a body placed upon said support means for rotating the said support means and the said body by rotation of said roller means.

4. A device according to claim 1, wherein the said beam-splitting means comprise a plate member having a pair of slots therethrough, said slots being correlated to extend across a predetermined part of the width of said body.

5. A device according to claim 1, wherein amplifying means are disposed between the radiation sensitive means and the indicating means.

6. A device according to claim 1 further comprising resistance bridge means connected in circuit with said radiation sensitive means so as to neutralize leakage currents generated by said radiation sensitive means when impinged upon by a uniform radiation.

7. A device according to claim 1, wherein said compensating means is mounted on said support means for axial movement in unison therewith.

8. A device according to claim 1, wherein said wall member is in the form of a stepped plate disposed between said source of radiation and said support means, the stepping of said plate compensating for the variations in the diameter of the wall of said body.

9. A device according to claim 1 and further comprising switch means for connecting the indicating means with and disconnecting the same from the radiation sensitive means, said switch means being controlled by the axial movement of said support means.

10. An apparatus for gauging the dimensions of an object of irregular contour comprising, a source of penetrating radiations, means for directing a beam of said radiations in a predetermined path, a detector located in the path of said beam, means for supporting an object formed with a portion having irregularly varying dimensions at different points measured in the same direction for the passage of the beam therethrough in said direct-ion in the gauging of said dimensions, and a monitor supported in the path of said beam tor the passage of the beam therethrough simultaneously with its passage through the object and having a portion located in a predetermined opposed position with relation to said object in the direction of the dime of the beam the dimensions of which, at diiferent points, measured in the direction of the :line of the beam, vary in inverse relation to the dimensions of said portion of the object under test at corresponding opposed points and, the dimension of which portion at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction is always equal to a constant sum if the object is a perfect object.

11. An apparatus for gauging the dimensions of an object of irregular contour comprising, a source of penetrating radiations, means for directing a beam of said radiations in a predetermined path, a detector located in the path of said beam, means for supporting an object formed with a portion having irregularly varying dimensions at diiferent points measured in the same direction for the passage of the beam therethrough in said direc tion in the gauging of said dimensions, a monitor of solid material supported in the path of said beam for the passage of the beam therethrough simultaneously with its passage through the object and having a portion located in a predetermined opposed position with relation to said object in the direction of the line of the beam the dimensions of which, at diiferent points, measured in the direction of the line of the beam, vary in inverse relation to the dimensions of said portion of the object under test at corresponding opposed points and, the dimension of which portion at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed poin in said direction is always equal to a constant sum if the object is a perfect object, and means for causing the beam to traverse a predetermined scanning pattern on the object under test and the monitor.

12. An apparatus for gauging the dimensions of an object of irregular contour comprising, a source of penetrating radiations, means for directing a beam of said radiations in a predetermined path, a detector located in the path of said beam, means for supporting an object formed with a portion having irregularly varying dimensions at different points measured in the same direction for the passage of the beam therethrough in said direction in the gauging of said dimensions, a monitor of solid material supported in the path of said beam for the passage of the beam therethrough simultaneously with its passage through the object and having a portion located in a predetermined opposed position with relation to said object in the direction of the line of the beam the dimensions of which, at diiferent points, measured in the direction of the line of the beam, vary in inverse relation to the dimensions of said portion of the object under test at corresponding opposed points and, the dimension of which portion at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction is always equal to a constant sum if the object is a perfect object, and means for moving the object under test and the monitor together transversely of the beam to cause the beam to traverse a predetermined scanning pattern on the object under test and the monitor.

13. An apparatus for gauging the thickness of an object of irregular contour comprising, a source of penetrating radiations, means for directing a beam of said radiations in a predetermined path, a detector located in the path of said beam, means for supporting an object formed with a portion having an irregularly variable thickness in the path of said beam in position for the passage of the beam through said portion in the direction of the thickness thereof in the gauging operations, and a monitor supported in the path of said beam in position for the passage of the beam therethrough in the direction of the thickness thereof simultaneously with its passage through the object and having a portion located in a predetermined opposed position with relation to said portion of the object in the direction of the line of the beam, the thickness of which portion of the monitor at each point therein added to the thickness of said portion of the object at an opposed point in said direction is always equal to a constant sum, if the object is a perfect object.

14. An apparatus for gauging the dimensions of an object of irregular contour comprising, a source of penetrating radiations, means for directing a beam of said radiations in a predetermined path, a detector located in the path of said beam, means for supporting an object formed with a portion having irregularly varying dimensions at different points measured in the same direction for the passage of the beam therethrough in said direction in the gauging of said dimensions, a monitor of solid material supported in the path of said beam for the passage of the beam therethrough simultaneously with its passage through the object and having a portion located in a predetermined opposed position with relation to said object in the direction of the line of the beam the dimensions of which, at different points, measured in the direction of the line of the beam, vary in inverse relation to the dimensions of said portion of the object under test at corresponding opposed points and, the dimension of which portion at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction is always equal to a constant sum, if the object is a perfect object, and means by which the piece and the monitor may berelatively adjusted to locate the said portion of the monitor in said predetermined opposed position with relation to said piece in the direction of the line of the beam.

15. An apparatus for gauging the dimensions of an object of irregular contour comprising means for producing and projecting in a predetermined direction a beam of penetrating radiations, means for supporting an object of irregular contour and a monitor for said piece in predetermined opposed relation in the path of said beam, the dimension of the monitor at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction being always equal to a constant sum if the dimensions of the object are correct, said supporting means including a carriage mounted for movement in opposite directions, a second carriage mounted on said first carriage for movements in opposite directions transverse to the movements of the first carriage, upon which second carriage one of said means is mounted, means for imparting to the first carriage a continuous movement in one direction during a scanning operation, means for imparting to the second carriage a plurality of movements in opposite directions during a scanning operation and machine actuated and controlled mechanism for controlling said imparting means whereby the beam is caused totraverse a scanning pattern on the piece and the monitor. 7

16. An apparatus for gauging the dimensions of an object of irregular contour comprising a source of penetrating radiations, means for directing a beam of said radiations from said source in a predetermined path, a detector located in the path of said beam, means for supporting a piece under test and a monitor in predetermined opposed relation for the. passage of the beam simultaneously therethrough, the dimension of the monitor at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction being always equal to a constant sum if the dimensions of the object are correct, said supporting means including a carriage mounted for continuous movement in one direction during a scanning operation, a second carriage mounted on said first carriage for movement therewith and for movement independently of said first carriage in opposite directions transverse to the direction of movement of said first carriage upon which second carriage the piece under test and the monitor are mounted, and machine actuated means for moving said carriage and controlling the movements thereof to cause the beam to traverse a scanning pattern with relation to said piece under test and the monitor.

17. An apparatus for gauging the dimensions of an object of irregular contour comprising a source of penetrating radiations, means for directing a beam of said radiations from said source in a predetermined path, a detector located in the path of said beam, means for supporting a piece under test and a monitor in predetermined opposed relation for the passage of the beam simultaneously therethrough, the dimension of the monitor at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction being always equal to a constant sum if the dimensions of the object are correct, said supporting means including a carriage mounted for continuous movement in one direction during a scanning operation, a second carriage mounted on said first carriage for movement therewith and for movement independently of said first carriage in opposite directions transverse to the direction of movement of said first carriage upon which second carriage the piece under test and the monitor are mounted, and means for moving said carriages to cause the beam to traverse a scanning pattern with relation to said piece under test and the monitor including an electric drive means for driving said first carriage, a second electric drive means for driving the second carriage, connected circuits for said drive means and machine actuated means for controlling said circuits.

18. An apparatus for gauging the dimensions of an object of irregular contour comprising a source of penetrating radiations, means for directing a beam of said radiations from said source in a predetermined path, a detector located in the path of said beam, means for supporting a piece under test and a monitor in a predetermined opposed relation for the passage of the beam simultaneously therethrough, the dimension of the monitor at each point therein in the direction of the line of the beam added to the dimension of the object at each opposed point in said direction being always equal to a constant sum if the dimensions of the object are correct, said supporting means including a carriage mounted for continuous movement in one direction during a scanning operation, a second carriage mounted on said first carriage for movement therewith and for movement independently of said first carriage in opposite directions transverse to the direction of movement of said first carriage upon which second carriage the piece under test and the monitor are mounted, and means for moving said carriages to cause the beam to traverse a scanning pattern with relation to said piece under test and the monitor including an electric drive means for driving said first carriage, a second electric drive means for driving the second carriage, connected circuits for said drive means, a manually controlled switch for producing a reversal of the direction of the current through the first drive means, and an automatically controlled switch for producing a reversal of the direction of the current through the second drive means.

19. An apparatus for gauging the dimensions of an object of irregular contour comprising, a source of penetrating radiations, means for directing a beam of said radiations in a predetermined substantially horizontal path, a detector located in the path of said beam, means for supporting a piece of irregular contour in the path of said beam in a position for the gauging of predetermined dimensions of said piece in the direction of the line of the beam, and a monitor supported in the path of said beam in a predetermined opposed position with relation to the object, the dimension of the monitor at each point therein the direction of the line of the beam added to the dimension of the object at each opposed point in said direction being always equal to a constant sum if the dimensions of the object are correct, the apparatus having provision for adjustment to adjust the angle, about a vertical axis, at which the beam passes through the piece.

20. A method of gauging the dimension of an object of irregular contour formed with a portion having irregularly varying dimensions in a predetermined direction comprising producing a monitor provided with a portion so formed that when the monitor is placed in a predetermined position with relation to the object with said portion of the monitor in predetermined opposed relation to said portion of the object, the sum of the dimension of the said portion of the object at each point therein in said direction added to the dimension in the same direction of said portion of the monitor at an opposed point therein is always equal to a constant if the object is a perfect object, and passing a beam of penetrative radiation through said object and said monitor in said direction to gauge the combined dimensions of the object and the monitor.

21. A method of gauging the dimensions of an object of irregular contour formed with a portion having irregularly varying dimensions in a predetermined direction comprising producing a monitor provided with a portion so formed that when the monitor is placed in a predetermined position with relation to the object with said portion of the monitor in predetermined opposed relation to said portion of the object, the sum of the dimension of the said portion of the object at each point therein in said direction added to the dimension in the same direction of said portion of the monitor at an opposed point therein is always equal to a constant if the object is a perfect object, and passing a beam of penetrative radiations through said object and said monitor in said direction at a plurality of points to gauge the combined dimensions of the object and the monitor at each of said points.

22. A method of gauging the dimensions of an object of irregular contour formed with a portion having irregularly varying dimensions in a predetermined direction comprising producing a monitor provided with a portion so formed that when the monitor is placed in a predetermined position with relation to the object with said portion of the monitor in predetermined opposed relation to said portion of the object, the sum of the dimension of the said portion of the object at each point therein in said direction added to the dimension in the same direction of said portion of the monitor at an opposed point therein is always equal to a constant it the object is a perfect object, passing a beam of penetrative radiations through said object and said monitor in said direction at a plurality of points to gauge the combined dimensions of the object and the monitor at each of said points and indicating the extent of the unabsorbed radiations at each point.

References Cited in the file of this patent UNITED STATES PATENTS 2,097,760 Failla Nov. 2, 1937 2,264,725 Shoupp et 'al Dec. 2, 1941 2,301,251 Caper Nov. 10, 1942 2,467,812 Clapp Apr. 19, 1949 2,647,214 Penney et al July 28, 1953 2,670,401 Weinberg Feb. 23, 1954 2,679,317 Roop May 25, 1954 2,684,001 Wilson July 20, 1954 2,687,477 Pfaif Aug. 24, 1954 2,732,503 Jacobs Jan. 24, 1956 2,843,748 Jacobs July 15, 1958 2,870,336 Fountain Ian. 20, 1959 

